Silk-screen printing paste



Patented Sept. 9, 1952 SILK-SCREEN PRINTING PASTE Frank Enoch Kcrridge and Cyril Stanley Couper,

London, England, assignors to Johnson, Matthey & Company Limited, London, England, a

British company No Drawing. Application June '3, 1949, Serial No.

97,094. In Great Britain June 9, 1948 6 Claims. 106-26) This invention relates to improvements in and relating to the decoration of heat-resisting bases, that is to say bases capable of withstanding firing at a temperature of at least 400 C., such as glass, earthenware and china and is more particularly concerned with the decoration of such bases with a design or decoration in gold. See also our copending application 105,444, filed July 18, 1949.

Gold decorations on glass, china or earthenware have in general hitherto been produced by the use of v I (1) Liquid gold, which consists essentially of a solution of a sulphoresinate of gold in suitable solvents, and

(2) Liquid burnish gold a suspension of gold powder in essential oils, with or without the addition of liquid gold, an adhesion promoting agent, such as a lead borosilicate flux or a hismuth compound, and an extender, such as a mercury salt.

In the decoration oi articles with a single simple design in gold, each of the above materials may be applied by hand painting with subsequent firing.

When, however, a repetitive design is required to be applied to the ware, it is usual to apply the decoration by a printing method, namely rubber stamp printing or engraved plate printing.

Therubber stamp method, whilst being simple and-rapid in use, results in a design which is lacking in richness and sharpness of outline and, moreover, does not enable ceramic colours to be printed simultaneously in register with the gold.

With engraved plate or copper plate printing, a transfer is prepared by engraving or etching a designon a copper or glass plate, filling the Iinter-.

stices or depressions so formed with the gold printing paste, applying a sheet of gummed tissue paper, gummed side downwards, to the coated plate and then removing the paper, which now carries the design. To decorate an article, the paper is applied, whilstthe, paste is still moist or sticky with the design-carrying side downwards, to the article. The tissue paper is then soaked off and the article fired.

This method, in the hands of a skilled operator, givesa decoration of good quality, but, as the design is applied to the ware, in the moist state, it cannot beused for applying both gold and ceramic colour simultaneously in register. A further disadvantage is that transfers prepared by this. method cannot normally be stored for future 1.1Se."-."-" i It is also known to decorate'ware witha ceramic colour or vitreous enamelby applying directly to the ware a vitreous enamel or ceramic colour paste by means of the silk-screen printing method, and it has also been proposed to prepare a ceramic colour transfer by the silk-screen printing method.

Silk-screen printing, whether used for decorating an article by direct application or for the preparation of transfers, oiiers advantages over the other methods referred to in that the apparatus employed'is inexpensive, a variety of decorative effects are obtainable and prints of high quality and Well-defined outlines can be readily produced by relatively unskilled workers.

Pastes embodying the above-mentioned materials, as heretofore constituted for use with the rubber stamp or engraved plate printing methods are quite unsuited for use with the silk-screen printing method, particularly in the case of the preparation of transfers.

It will be appreciated from a consideration of the above that, if a gold paste were provided which could be satisfactorily applied by the silkscreen printing method, very considerable advantages would accrue both from the artistic and the commercial aspects. In the first place it would be possible to decorate an article with a design in gold which would have a more pleasing effect than those hitherto obtainable, owing to the improved definition of the outlines and the fact that it becomes possible to print a ceramic colour design in register with the gold, and. secondly the process of decorating can be carried out relatively inexpensively.

, Silk-screen printing, however, produces a very thick deposit and whilst this is, in many instances, particularly in the case of ceramic enamels, greatly to be desired, it may be that, in the case of a gold decoration, the cost of the gold may outweigh the advantages attainable by the use of this method. Attempts to produce a thinner deposit by employing a low gold: medium ratio in the paste, will result in unsatisfactory printing, owing to the low proportion of solid in the paste, and frequently in flowing of the prints and loss of sharpness of outline before drying.

An object of the invention, therefore, is to overcome the above disadvantages and to provide an improved gold paste consisting essentially of a metal powder-ceramic flux mixture containing gold powder or a mixture of gold powder and silver powder and suitable for direct application to an article to be decorated by the silk-screen printing method, or for the preparation, by the silk-screen printing method, of transfers intended for subsequent application to an article.

Another object is to enable a thin deposit of gold to be applied to a heat-resisting base by the silk-screen printing method.

A further object is to enable the thickness of the gold deposit to .be readily controllable and tone-effects ranging from red-gold to green-gold to be obtained as desired.

Another object is to provide a gold silk-screen printing paste for the preparation of a transfer.

or for direct application to a heat-resisting base, said paste including a volatilisable solid, which will volatilise without carbonising during the sub sequent firing of a heat-resistance base decorated with the paste.

A still further object is to provide a gold silkscreen printing paste comprising a mixture of gold powder, or a mixture of gold powder and silver powder, a volatilisable solid, a flux or adhesion promoting agent having a melting point no higher than 500 C. and an organic silk-screen printing medium or vehicle.

359 including a volatilisable solid in the paste, the amount of gold present in the paste, and hence the thickness of thefinal gold film obtained after firing, may be varied as desired, since by suitably proportioning the amount of volatilisable solidincluded, the ratio of liquid to total solids in the paste may be maintained in the correct proportion to give good printing qualities.

The volatilisable solid may consist of any solid which volatilises completely at a low temperature, but we have found that certain organic materials, such asoxanilide, acetanilide or anthracene are more suitable than volatilisable inorganic materials, such as ammonium chloride. Of the organic materialsmentioned, we prefer to use anthracene.

The proportion of medium to solid substances is preferably 1-4 parts of medium to 2 parts of solid, the exact proportions depending on the particle size of the solids and the viscosity of the medium.

The organic medium will comprise a film-forming ingredient dissolved in a solvent, for example it may be a cellulose derivative or a natural or synthetic resin or resins or a mixture thereof dissolved in a solvent or solvent mixture having a rate of evaporation suitable for silk-screen printing. For example, the medium may consist of nitrocellulose dissolved in amyl and/r ethyl lactate or of colophony dissolved in pine oil.

The gold powder employed may be of the kind produced by adding a reducing agent to a solution of a. gold compound or a powder produced by mechanical comminution of the metal may be used.

The flux may be a lead borosilicate or a lead alkali borosilicate flux or a bismuth compound, such as bismuth oxide or oxychloride.

If desired, an extender, such as a mercury salt, may be included in the paste. In this case, we prefer to use mercurous chloride.

Moreover, if desired, up to 20%, determined on the weight of gold in the paste, of silver powder or its equivalent of a silver compound, such as silver carbonate, may be included in order to give a greenish-yellow tone to the ultimately fired film.

If the paste is to be used to prepare a transfer, it will be found desirable to include in the medium a suitable plasticiser or plasticisers, such as methyl abietate and/or castor oil for the purpose of preventing cracking of the decoration during transferring or firing.

The following are examples of pastes prepared in accordance with the invention, for the 'decora-' tion of earthenware, containing a cellulose deriv ative-based and a resinous medium respectively.

Per cent by weight theconstituents being again ground together to form a paste.

In the case of the decoration of a glass article, owing to "the lower firing temperaturewhich is employed so as to avoid distortion of the lass, it will: befound necessary to" include a higher percentage of flux in the paste to ensure adequate adhesion. j I I I The preferred composition of-the individual constituents of the paste isas' ronowsz Flux or adhesion promotingconstituent Although many lead borosilicate or lead alkali borosilicate fluxes, which melt at atemperature of 400-500" C. or bismuth compounds may be used, we have found the most satisfactory results are obtained by using a flux having the following composition: r

7 Medium If a medium based on a cellulose derivative is employed, the following composition will be found suitable:

Per cent by weight If a resinousmedium is employed, the follow-v mg composition will be found suitable: V

. Per cent by weight Pine Colophony a- 2 0 Methyl abietate -l 5 Castor oil r 5 In the use of our improvedpasteior. thedecoration, for example, of a substantially flat article of glazed earthenware, the paste is applied to the article, so as to form any desired design thereon, by the silk-screen printing method, and allowed to dry. The coated article is then fired at a temperature within the range of 650-750" C. to burn away the, organic matter 'a'nd. cause t metallic gold to adhere firmly to the article.

If the base being decorated is of glass, the firing temperature is preferably between 500 0. and 650 0.

The decoration, after firing, will present. a.

matt surface, and may, if desired, be lightly scouredwith sand or burnished withagate so.

as to produce a bright effect.

When the paste is to be used for preparing a gold transfer, the paste is applied, in any desired design, to a sheet of transfer paper by the silk-screen printing method and is again allowed to dry. To decorate an article, the transfer paper, with the design thereon, is applied to the article and the design transferred to the surface thereof by the well-known slide-off" method. The article is then fired at a suitable temperature, i. e. within the range of SOD-650 C. in the case of a glass article, and 650-800 C. in the case of china or earthenware. The fired design may, in this case also, be lightly bur- 1 nished.

It is to be understood that our improved gold paste may be printed so as to register with vitreous enamels or ceramic colours in a combined gold and enamel decoration.

What we claim is:

1. A silk-screen printing paste for the preparation of a transfer or for direct application to a heat-resisting base, said paste comprising a mixture of gold powder, anthracene, a. ceramic flux and an organic vehicle consisting of 56% by weight of amyl lactate, 20% by weight of ethyl lactate, 8% by weight of nitrocellulose, 8% by weight of methyl abietate and 8% by weight of castor oil and the relative proportions of gold powder, ceramic flux and anthracene to liquid vehicle being always substantially 2 parts of solids to 1-4 parts of vehicle.

2. A silk-screen printing paste for the preparation of a transfer or for direct application to an earthenware base, said paste comprising a mixture of the following constituents in the following proportions by weight, namely:

Percent Gold powder 40 Mercurous chloride 8 Lead borosilicate flux 2 Anthracene 10 Solution containing plasticized nitrocellulose 40 3. A silk-screen printing paste for the preparation of a, transfer or for direct application to a heat-resisting base, said paste consisting essentially of a metal powder-ceramic flux mixture, said metal powder being chosen from the group consisting of gold powder and a mixture of gold powder and silver powder, and anthracene, said metal powder-ceramic flux mixture and anthracene constituting solid ingredients,

flux mixture and anthracene constituting solid ingredients, and an organic screening vehicle comprising nitrocellulose dissolved in a solvent selected from the group consisting of amyl lactate, ethyl lactate and mixtures thereof and the relative proportion of the combined amounts of gold powder-ceramic flu mixture and anthracene to liquid vehicle being always substantially 2 parts of solids to 14 parts of vehicle.

5. A silk-screen printing paste for the preparation of a transfer or for direct application to a heat-resisting base, said paste consisting essentially of a gold powder-lead borosilicate flux mixture and anthracene, said gold powder-lead borosilicate flux mixture and anthracene constituting solid ingredients, and an organic screening vehicle comprising nitrocellulose dis- I solved in a solvent selected from the group consisting of amyl lactate, ethyl lactate and mixtures thereof and the relative proportion of the combined amounts of gold powder-lead borosilicate flux mixture and anthracene to liquid vehicle being always substantially 2 parts of solids to 1-4 parts of liquid'vehicle.

67 A silk-screen printing paste for the preparation of a transfer or for direct application to a heat-resisting base, said paste consisting essentially of a gold powder-ceramic flux mixture, said flux being selected from the group consisting of bismuth oxide and bismuth oxychloride and anthracene, said gold powderceramic flux mixture andanthracene constituting solid ingredients, and an organic screening vehicle comprising nitrocellulose dissolved in a solvent selected from the group consisting of amyl lactate, ethyl lactate and mixtures thereof, and the relative proportion of the combined amounts of gold powder-ceramic flux mixture and anthracene to liquid vehicle being always substantially 2 parts of solids to 1-4 parts of vehicle.

FRANK ENOCH KERRIDGE. CYRIL STANLEY COUPER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 255,421 Dode Mar. 28, 1882 460,358 Buttler Sept. 29, 1891 1,752,462 Smith Apr. 1, 1930 2,113,449 Hoffman et al Apr. 5, 1938 2,190,210 Kaber Feb. 13, 1940 2,287,053 Murphy June 23, 1942 2,294,760 Morris Sept. 1, 1942 2,318,803 Schneider et al. May 11, 1943 2,452,805 Sussenbach Nov. 2, 1948 FOREIGN PATENTS Number Country Date 7,688 Great Britain 1892 9,261 Great Britain 1894 428,743 Great Britain May 17, '1935 526,853 Great Britain Sept. 26, 1940 566,718 Great Britain June 10, 1945 

3. A SILK-SCREEN PRINTING PASTE FOR THE PREPARATION OF A TRANSFER OR FOR DIRECT APPLICATION TO A HEAT-RESISTING BASE, SAID PASTE CONSISTING ESSENTIALLY OF A METAL POWDER-CERAMIC FLUX MIXTURE, SAID METAL POWDER BEING CHOSEN FROM THE GROUP CONSISTING OF GOLD POWDER AND A MIXTURE OF GOLD POWDER AND SILVER POWDER, AND ANTHRACENE, SAID METAL POWDER-CERAMIC FLUX MIXTURE AND ANTHRACENE CONSTITUTING SOLID INGREDIENTS, AND AN ORGANIC SCREENING VEHICLE COMPRISING NITROCELLULOSE DISSOLVED IN A SOLVENT SELECTED FROM THE GROUP CONSISTING OF AMYL LACTATE, ETHYL LACTATE AND MIXTURES THEREOF, AND THE RELATIVE PROPORTION OF THE COMBINED AMOUNTS OF METAL POWDER-CERAMIC FLUX MIXTURE AND ANTHRACENE TO LIQUID VEHICEL BEING ALWAYS SUBSTANTIALLY 2 PARTS OF SOLIDS TO 1-4 PARTS OF VEHICLE. 